The invention relates to a clutch release bearing in contact with a disk spring, wherein the clutch release bearing has at least one curved contact surface, which is located at a radial distance from the axis of rotation of the clutch release bearing and which is used for contacting at least one end of at least one spring tongue of the disk spring.
DE 37 438 53 A1 describes a clutch release bearing of the class-defining type. The contact surface is constructed either on the inner ring or on an outer ring of the clutch release bearing. The ends of the spring tongues are in touching contact with the contact surface. Here, the contact surface is either an annular surface extending about the axis of rotation or alternatively several segment-like contact surfaces adjacent to each other on the peripheral side are constructed on the clutch release bearing. If several of the segment-like contact surfaces are constructed on the clutch release bearing, as described in DE 37 438 53 A1, for example, ribs are provided between the contact surfaces for engagement between the spring tongues.
When the clutch disengages, the peripheral contact surface on the bearing ring of the release bearing is pressed with force onto the spring tongue(s). The spring tongues therefore move in the axial direction. The contact, at which the spring tongues meet the contact surface, shifts during the moving on the contact surface radially inward in the direction of the axis of rotation of the release bearing or radially away from the axis of rotation. The contact also shifts with increasing wear in the clutch.
The ends of the spring tongues meeting the contact surface are therefore often curved, so that they bulge convexly outward to the contact surface on the bearing and so that these always run with a linear contact to the contact surface often also curved convexly in the direction of the end on the spring tongue during the inward and outward yielding. An example of such a release bearing arrangement is described in DE 37 438 53 A1.
However, there are also clutch or vehicle manufacturers that, for various reasons, use disk springs, whose ends of the spring tongues are constructed straight. Such a release bearing arrangement is described in EP 015 383 59 A1. The ends usually stand in contact with a curved contact surface. These release bearing arrangements as a rule have an optimum linear contact at only one operating point, wherein this linear contact transforms into a two-point contact in a radial direction and becomes increasingly less in the other radial direction and finally ends at a single-point contact. When the clutch is actuated, the contact is shifted radially outward into a single-point contact and for movement due to wear it is shifted into a two-point contact. Such reductions of the contact lead to high surface pressures and promote unacceptable wear due to the contact on the contact and touching faces. The contact effects on the release bearing arrangements of the state of the art are described with FIGS. 1 and 2.
FIG. 1 shows schematically the touching and contact relationships during the contact of a spring tongue for the release bearing arrangement as described in EP 015 383 59 A1. As an example, a part of an outer surface of a toroidal body 1 is considered as the curved contact surface. The toroidal body 1 is shown simplified by grid lines 2 and 3. The axial bulge of the contact surface is symbolized by the grid lines 2. The grid lines 2 run in planes, in which the axis of rotation 4 extends and which are aligned with the axis of rotation 4. Peripheral curvatures of the contact surface in planes, which are intersected at a right angle by the axis of rotation 4, are symbolized by the grid lines 3. The contact face of the non-curved end of a spring tongue is symbolized with the surface 5.
The surface line marked with 3.1 symbolizes the surface line 3.1 projecting farthest in the axial direction at the axial peak 3.1 of the contact surface. In FIG. 2, a longitudinal section through the body along the axis of rotation 4, the surface line 3.1 marks the turn-around point (peak) of a curve described in the longitudinal section by one of the grid lines 2.
The contact of the face 5 with the surface line 3.1 at the peak of the curve results in an optimum linear contact 6. The line described by the linear contact 6 is curved in FIG. 1 corresponding to the profile of the surface line 3.1. If the surface 5 tilted in the direction of the arrow 7 extends on the contact surface, in the end a two-point contact with the contacts 8 and 9 is produced. If the face 5 tilted in the direction of the arrow 10 extends on the contact surface, the linear contact becomes increasingly smaller until the face 5 and the contact surface are finally in a single-point contact at point 11.